This disclosure is based upon, and claims priority from French Application No. 98/16140, filed on Dec. 21, 1998 and International Application No. PCT/FR99/02942, filed Nov. 29, 1999, which was published on Jun. 29, 2000 in a language other than English, the contents of which are incorporated herein by reference.
The present invention concerns the field of portable items such as contactless chip cards having a card body, an electronic module and, connected to said module, an antenna. The invention concerns more particularly a method for making such cards.
Such cards are designed for carrying out diverse operations such as, for example, banking operations, telephone communications, or diverse identification operations. They are designed, in particular, for remote transaction operations in which they are debited remotely by a certain number of units when passed close to a terminal and where they can also be recharged remotely.
These operations take place by means of remote electromagnetic coupling (in general of inductive type) between the card electronics and a receiving device or reader. This coupling takes place in read mode or in read/write mode and the data transmission takes place by means of radio-frequencies or ultrahigh frequencies.
Chip cards, whether with and/or without contacts, are produced to standardized dimensions. A common standard, but not limitative for the present invention, is that referred to as ISO 7810 which corresponds to a card of standard format, 85 mm in length, 54 mm in width, and 0.76 mm thick.
A method of producing contactless chip cards using a cold lamination technique is known. Such a method is shown schematically in FIG. 1A. In this case, an electronic assembly, also referred to as a transponder, composed of an antenna 5 made of a wound wire connected to an electronic module 7, is disposed above a first plastic sheet 1. Then a liquid resin 8, for example made of polyurethane, is dispensed so as to embed the electronic assembly. A final step then consists of covering the resin 8 with an upper plastic sheet 6 and then of performing a cold lamination in order to weld the resin 8 to the lower sheet 1 and upper sheet 6.
In a variant implementation illustrated in FIG. 1B, the electronic assembly can be composed of a printed circuit type wafer 30 comprising an antenna 31, produced by lamination, overlaying, etching or silk screen printing, and a chip or a module 40 connected to said antenna 31.
In both these cases, connection of the module to the antenna is carried out by means of a tin/lead solder, by an ultrasonic weld, by thermocompression or by means of a conductive glue for example.
This method, whatever the variant used, has however a number of drawbacks. A first drawback is related to the fact that the electronic assembly is not fully immovably attached to one of the outer sheets of the card. Consequently, sometimes the indexing of the electronic assembly is shifted with respect to the outer sheets. This shift can lead to the cutting and destruction of the electronic assembly, at the time the sheets are cut to the card format, when said sheets were not cut beforehand. In addition, the manipulation of three independent elements is necessary: two outer sheets 1 and 6 and an electronic assembly.
Moreover, when the liquid resin is being dispensed, air bubbles form around the electronic assembly. These air bubbles lead to the creation of defects at the surface of the card. These surface defects are not only unsightly but they also involve difficulties during the printing step for decorating and personalizing the card. This is because the surface defects create depressions which locally prevent the transfer of material, with the result that it is difficult to produce a good quality print over the whole surface of the cards. These surface defects also have a tendency to spread and grow larger during ageing of the card, as a result of temperature variations undergone by said card.
Another method for making contactless chip cards which has been envisaged by the inventors is illustrated in FIG. 2. This method consists of producing an antenna 11 on the face of one of the two outer sheets 10 and then of connecting a chip 20 to the antenna. The antenna 11 is for example produced by silk screen printing, lamination or overlaying of a conductive wire. It comes in the form of a spiral, at the ends of which there are provided connection terminals 15. The chip 20 is for example transferred so that its non-active rear face is directly glued to the antenna by means of an insulating glue 25. An electrical connection is made by means of an electrically conductive resin 27 which is dispensed on to both the connection terminals 15 and the contact pads 21. A liquid resin 18 is then dispensed on to the electronic assembly, and then an upper sheet 16 is transferred and welded to the first sheet 10 by cold lamination. In this case, the number of independent elements manipulated is reduced to 2. These elements are constituted by the first outer sheet 10, immovably attached to the electronic assembly, and by the second outer sheet 16.
This method, however, would also have drawbacks. It would not allow, notably, the use of a module under good operating conditions, but only that of a chip. This is because, if a module were used, it would be transferred so that its metallic grid, having contact areas, is oriented towards the tracks of the antenna. An insulating glue makes it possible to fix the module on to the tracks of the antenna while avoiding the appearance of short circuits between this antenna and the metallic grid of the module. Contact areas of the metallic grid of the module are directly connected to the connection terminals of the antenna. However, in this case, it would be very difficult to have control over the insulation, on the one hand between the tracks of the antenna, and on the other hand, between the antenna and the metallic grid of the module.
Finally, the insulating glue, used for fixing the module and insulating it electrically from the antenna turns, is not always distributed correctly between the tracks of the antenna, with the result that air bubbles can form around the module. These air bubbles lead to the creation of defects at the surface of the card, which are unsightly and involve difficulties during the card printing and personalization step.
One aim of the invention consists of making a contactless chip card, having an electronic module connected to an antenna, the production of this card requiring the manipulation only of two independent elements, and making it possible to overcome the drawbacks related to the methods of the prior art.
A more particular object of the invention is a method for making a contactless chip support, comprising an electronic assembly, having an antenna and at least one microcircuit connected to the antenna, said electronic assembly being embedded in a body of the support composed of laminated sheets, characterised in that it has the following steps:
producing the antenna on a first support sheet, said antenna forming a spiral at the ends of which there are provided connection terminals,
producing an insulating bridge partly covering the antenna turns with the exception of at least part of the connection terminals,
depositing a drop of filling material on the insulating bridge,
transferring the microcircuit against the insulating bridge and the filling material, and establishing an electrical connection from the microcircuit to the connection terminals of the antenna.
According to another characteristic, the method has a step consisting of:
transferring a second sheet against the previously formed electronic assembly and performing a lamination of said first and second sheets.
By virtue of the method according to the invention, there are only two independent elements left to be manipulated, that is to say the two outer sheets. Since the electronic assembly is immovably attached to one of the outer sheets, the indexing problems are no longer posed. The insulating bridge provides electrical insulation of the antenna tracks and of the metallic grid of the module. It also makes it possible to drive out the residual air located between the tracks of the antenna. The filling material fills in the space between the module and the insulating bridge and makes it possible to drive out the residual air around the module. With the residual air being driven out, the appearance of air bubbles and surface defects is avoided.
The filling material is for example a cyanoacrylate-based glue.
According to another characteristic of the invention, the insulating bridge has a substantially rectangular form and has two notches at two given locations in order to allow exposure of the connection terminals of the antenna. This insulating bridge is preferably produced by silk screen printing of a liquid resin, and then polymerization under ultraviolet radiation. It preferably has a thickness between 15 and 60 xcexcm.
According to another characteristic of the invention, the electrical connection between the module and the antenna is implemented by means of an electrically conductive glue which is deposited on the connection terminals of the antenna.
According to another characteristic of the invention, the electronic module can also be replaced by an integrated circuit chip.
According to another characteristic, the microcircuit is placed in an electronic module so that the metallic contact areas are disposed against the insulating bridge and the filling material.
Another object of the invention also concerns a contactless chip card, having an electronic assembly constituted by an electronic module and, connected to said module, an antenna, said electronic assembly being embedded in the body of the card, characterised in that the electronic assembly is fixed on a first support sheet, the antenna being produced on said first support sheet, and the module being transferred so that its metallic contact areas are disposed facing the antenna turns; an insulating bridge, covered with a filling material, being disposed between the module and the turns of the antenna, said insulating bridge having a geometry such that it does not cover the connection terminals of the antenna in order to allow the establishment of an electrical connection with the electronic module.